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David Axon
David John Axon (1951 – 5 April 2012) was a British astrophysicist specialising in observations of active galactic nuclei. He was a professor at the University of Hertfordshire and the Rochester Institute of Technology (RIT), and at the time of his death was Head of the School of Mathematical and Physical Sciences at the University of Sussex. Early life David Axon was born in Doncaster in the county of Yorkshire, England, to an English father and Welsh mother. He studied at the University of Durham (Hatfield College), where he earned a BSc in Physics in 1972. In 1978 he completed his Ph.D. at the same institution under the direction of Arnold Wolfendale. He subsequently held research fellowships at the University of Sussex, University College London and the Institute of Astronomy at the University of Cambridge. Career In 1983 Axon was appointed to a faculty position at the University of Manchester where he taught Physics and carried out research at the Nuffield Radio Ast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy
Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest include planets, natural satellite, moons, stars, nebulae, galaxy, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond atmosphere of Earth, Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonian astronomy, Babylonians, Greek astronomy, Greeks, Indian astronomy, Indians, Egyptian astronomy, Egyptians, Chinese astronomy, Chinese, Maya civilization, Maya, and many anc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Institute Of Astronomy, Cambridge
The Institute of Astronomy (IoA) is the largest of the three astronomy departments in the University of Cambridge, and one of the largest astronomy sites in the United Kingdom. Around 180 academics, postdocs, visitors and assistant staff work at the department. Research at the department is made in a number of scientific areas, including exoplanets, stars, star clusters, cosmology, gravitational-wave astronomy, the high-redshift universe, AGN, galaxies and galaxy clusters. This is a mixture of observational astronomy, over the entire electromagnetic spectrum, computational theoretical astronomy, and analytic theoretical research. The Kavli Institute for Cosmology is also located on the department site. This institute has an emphasis on ''The Universe at High Redshifts''. The Cavendish Astrophysics Group are based in the Battcock Centre, a building in the same grounds. History The institute was formed in 1972 from the amalgamation of earlier institutions: * The University ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2012 Deaths
This is a list of deaths of notable people, organised by year. New deaths articles are added to their respective month (e.g., Deaths in ) and then linked here. 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 See also * Lists of deaths by day The following pages, corresponding to the Gregorian calendar, list the historical events, births, deaths, and holidays and observances of the specified day of the year: Footnotes See also * Leap year * List of calendars * List of non-standard ... * Deaths by year {{DEFAULTSORT:deaths by year ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1951 Births
Events January * January 4 – Korean War: Third Battle of Seoul – Chinese and North Korean forces capture Seoul for the second time (having lost the Second Battle of Seoul in September 1950). * January 9 – The Government of the United Kingdom announces abandonment of the Tanganyika groundnut scheme for the cultivation of peanuts in the Tanganyika Territory, with the writing off of £36.5M debt. * January 15 – In a court in West Germany, Ilse Koch, The "Witch of Buchenwald", wife of the commandant of the Buchenwald concentration camp, is sentenced to life imprisonment. * January 20 – Winter of Terror: Avalanches in the Alps kill 240 and bury 45,000 for a time, in Switzerland, Austria and Italy. * January 21 – Mount Lamington in Papua New Guinea erupts catastrophically, killing nearly 3,000 people and causing great devastation in Oro Province. * January 25 – Dutch author Anne de Vries releases the first volume of his children's novel '' Journey Through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Young Stellar Object
Young stellar object (YSO) denotes a star in its early stage of evolution. This class consists of two groups of objects: protostars and pre-main-sequence stars. Classification by spectral energy distribution A star forms by accumulation of material that falls in to a protostar from a circumstellar disk or envelope. Material in the disk is cooler than the surface of the protostar, so it radiates at longer wavelengths of light producing excess infrared emission. As material in the disk is depleted, the infrared excess decreases. Thus, YSOs are usually classified into evolutionary stages based on the slope of their spectral energy distribution in the mid-infrared, using a scheme introduced by Lada (1987). He proposed three classes (I, II and III), based on the values of intervals of spectral index \alpha \,: \alpha=\frac. Here \lambda \, is wavelength, and F_\lambda is flux density. The \alpha \, is calculated in the wavelength interval of 2.2–20 m ( near- and mid-infrared reg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relativistic Jet
An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as an extended beam along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity. The formation and powering of astrophysical jets are highly complex phenomena that are associated with many types of high-energy astronomical sources. They likely arise from dynamic interactions within accretion disks, whose active processes are commonly connected with compact central objects such as black holes, neutron stars or pulsars. One explanation is that tangled magnetic fields are organised to aim two diametrically opposing beams away from the central source by angles only several degrees wide Jets may also be influenced by a general relativity effect known as frame-dragging. Most of the largest and most active jets are created by supermassive black holes (SMB ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: paramagnetism, diamagnetism, and antiferromagnetism, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a function assigning a vector to each point of space, cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galactic Superwind
A galactic superwind, or just galactic wind, is a high velocity stellar wind emanating from either newly formed massive stars, spiral density waves, or as the result of the effects of supermassive black holes. They are normally observed in starburst galaxies. Description Galactic winds are strong stellar winds made up of charged particles, ejecta, and varying amounts of hot and cool gas, interacting with enough force that the ejecta's kinetic energy is converted to thermal energy. The resulting effect is a massive gust of rapidly expanding super-heated gases that can span the length of a galaxy. In galaxies with active galactic nuclei, galactic winds can also be driven by the effects of super-massive black holes. Galactic winds are considered an important function in the evolution of a galaxy.{{cite book, last1=Heckman, first1=Timothy M., last2=Thompson, first2=Todd A., title=Handbook of Supernovae, date=2017, publisher=Springer, Cham, isbn=9783319218458, pages=2431–2454, la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BL Lac Object
A BL Lacertae object or BL Lac object is a type of active galactic nucleus (AGN) or a galaxy with such an AGN, named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization. Because of these properties, the prototype of the class ( BL Lac) was originally thought to be a variable star. When compared to the more luminous active nuclei ( quasars) with strong emission lines, BL Lac objects have spectra dominated by a relatively featureless non-thermal emission continuum over the entire electromagnetic range. This lack of spectral lines historically hindered identification of the nature and distance of such objects. In the unified scheme of radio-loud active galactic nuclei, the observed nuclear phenomenology of BL Lacs is interpreted as being due to the effects of the relativistic jet closely aligned to the line of sight of the observer. BL Lac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz ( to ) and energies in the range 145 eV to 124 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it on November 8, 1895. He named it ''X-radiation'' to signify an unknown type of radiation.Novelline, Robert (1997). ''Squire's Fundamentals of Radiology''. Harvard University Press. 5th edition. . Spellings of ''X-ray(s)'' in English include the variants ''x-ray(s)'', ''xray(s)'', and ''X ray(s)''. The most familiar use of X-rays is checking for fractures (broken bones), but X-rays are also used in other ways. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarimetry
Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Typically polarimetry is done on electromagnetic waves that have traveled through or have been reflected, refracted or diffracted by some material in order to characterize that object. Plane polarized light: According to the wave theory of light, an ordinary ray of light is considered to be vibrating in all planes of right angles to the direction of its propagation. If this ordinary ray of light is passed through a nicol prism, the emergent ray has its vibration only in one plane. Applications Polarimetry of thin films and surfaces is commonly known as ellipsometry. Polarimetry is used in remote sensing applications, such as planetary science, astronomy, and weather radar. Polarimetry can also be included in computational analysis of waves. For example, radars often consider wave polarization in post-processing to imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NICMOS
The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is a scientific instrument for infrared astronomy, installed on the Hubble Space Telescope (HST), operating from 1997 to 1999, and from 2002 to 2008. Images produced by NICMOS contain data from the near-infrared part of the light spectrum. NICMOS was conceived and designed by the NICMOS Instrument Definition Team centered at Steward Observatory, University of Arizona, USA. NICMOS is an imager and spectrometer built by Ball Aerospace & Technologies Corp. that allows the HST to observe infrared light, with wavelengths between 0.8 and 2.4 micrometers, providing imaging and slitless spectrophotometric capabilities. NICMOS contains three near-infrared detectors in three optical channels providing high (~ 0.1 arcsecond) resolution, coronagraphic and polarimetric imaging, and slitless spectroscopy in 11-, 19-, and 52-arcsecond square fields of view. Each optical channel contains a 256×256 pixel photodiode array of mercury ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
